Chair base swivel arrangement

ABSTRACT

A chair base swivel arrangement comprising a tubular member supported in upright position from a chair base and carrying at its upper end an axially split O-shaped bearing element of antifriction material that is engaged by a sintered swivel member on which the chair base nut or hand wheel rests. The bearing element seats of the tubular member and swivel member are of complemental semi-torus configuration relative to the bearing element peripheral surface, with the tubular member seat engaging the lower radially outer quadrant of the bearing element and the swivel member seat engaging the upper radially inner quadrant of the bearing element.

Driscoll et al.

[45] Dec. 11, 1973 [54] CHAIR BASE SWIVEL ARRANGEMENT [75] Inventors:Richard P. Driscoll, Clarendon Hills; James W. Lannert, Oswego; DonaldV. Beaver, Brookfield, all of Ill.

[73] Assignee: All-Steel Equipment Inc., Aurora,

Y lll,

[22] Filed: July 26, 1971 [2l] Appl. No.: 166,099

[52] U.S. Cl. 248/406, 308/230 [5l] Int. Cl. F16m 11/00, Fl6m 13/00 [58]Field of Search 248/405, 406, 415, 248/418, 425, 161; 308/230, DIG. 7;10S/139 [56] i References Cited UNITED STATES PATENTS 674,912 5/'1901Ellenbecker 248/405 2,999,665 9/1961 Ericson et al... 248/405 3,059,88810/1962 Lie.' 248/415 3,086,826 4/1963 `Gunnell 30S/DIG. 7 3,148,8559/1964 Hamilton 248/405 3,l67,366 l/l965 Freund 30S/DIG. 7 3,343,9019/l967 Marcus 1087139 3,503,523 3/1970 Hamilton et al 24S/425 3,606,2349/l97l Prescott 24S/406 Primary Examiner-Marion Parsons, Jr.

Attorney-Robert C. Brown, Jr. et al.

[57] ABSTRACT A chair base swivel arrangement comprising a tubularmember supported in upright position from a chair base and carrying atits 4upper end an axially split O- shaped bearing element ofantifriction material that is engaged by a sintered swivel member onwhich the chair base iiut or hand wheel rests. The bearing element seatsof the tubular member and swivel member are of complementa] semi-torusconfiguration relative Ito the bearing element peripheral surface, withthe tubular member seat engaging the lower radially outer quadrant ofthe bearing elementand the swivel member seat engaging the upperradially inner quadrant of the bearing element. v

8 Claims, 8 Drawing Figures CHAIR BASE SWIVEL ARRANGEMENT The presentinvention relates to a chair base swivel arrangement, and moreparticularly to a swiveling arrangement for swivel type chairs throughwhich the chair seat is rotatably supported on its base.

The familiar swivel chair is an item of office furniture that is subjectto extensive use in the office, and one of the parts of same that issubject to severe wear is the swivel mounting arrangement for swivelablysupporting the chair seat on its base. The swivel arrangements involvedrequire a special bearing arrangement that must furnish support for thechair seat, yet swing freely and still permit vertical adjustment foruser comfort.

Conventional bearing arrangements for swivel chairs frequently involve asteel on steel approach that requires adequate lubrication to remainfunctional. Some attempt has been made to utilize plastic and ballbearing elements as part of the bearing arrangement to reducelubrication requirements, but these arrangements have been subject toobjections either because of high cost or inconsistent results.

The principal object of this invention is to provide a swivelarrangement for swivel chairs that brings into the chair swivel bearingthe self-lubricating benefits available with selected plastic materials,while permitting a low cost, rugged design for mass production purposes.

Yet another principal object of the invention is to provide a swivelbearing arrangement for office chairs employing a simple plastic bearingelement that consistently meets endurance test requirements withoutpresenting undue lubrication needs or expensive preventative design.

Other objects of the invention are to provide a swivel arrangement foroffice chairs and the like that is readily adaptable for application toexisting chair bases, that does not compromise the desired adjustabilityin chair seat height, and that is economical of manufacture, convenientto install, and long lived in use.

In accordance with this invention, the swivel arrangement comprises anupright bearing tube and sintered swivel member arrangement cooperatingwith a bearing element of O-ring or torus shape formed from a suitableself-lubricating plastic material, in which the bearing tube and swivelmember have bearing seats making the actual Contact with the bearingelement which complement the shape of the bearing element and providetwo available slip or wear surfaces about which the chair seat mayswivel. The swivel member may be oil impregnated to reduce greasingrequirements, and the bearing unit is enclosed for maximum protectionagainst fouling.

Other objects, uses and advantages will be ovbious or become apparentfrom a consideration of the following detailed description and theapplication drawings in which like reference numerals indicate likeparts throughout the several views.

In the drawings:

FIG. 1 is an elevational view of a swivel chair base arranged inaccordance with the present invention, with parts shown in section andbroken away to expose other parts;

FIG. 2 is an exploded side elevational view, on a smaller scale, of theprincipal components of the chair base swivel arrangement shown in FIG.l;

FIG. 3 is a top plan view of the swivel member that rests on thebearingelement of this invention, and that is keyed to the chair spindleto preclude relative rotational movement between the two;

FIG. 4 is a cross-sectional view substantially along line 4-4 of FIG. 3;

FIG. 5 is a sectional view through the hand wheel or nut employed in thechair swivel arrangement of FIGS. 1 and 2;

FIG. 6 is a bottom plan view of the hand wheel shown in FIG. 5, asviewed along line 6-6 of FIG. 5;

FIG. 7 is a plan view of the bearing element employed in accordance withthis invention; and

FIG. 8 is a sectional view illustrating a modified form of swivelbearing arrangement in accordance with this invention.

However, it is to be understood that the specific drawing illustrationsprovided are supplied primarily to comply with the requirements of thePatent Law, and the invention has other embodiments which will beobvious to those skilled in the art, and which are intended to becovered by the appended claims.

GENERAL DESCRIPTION Reference numeral 10 of FIGS. 1 and 2 generallyindicates one embodiment of the invention which comprises a bearing tube12 supported by chair base 14 and defining at its upper end 16 a bearingretaining portion 18 in which is seated a bearing element 20 that isgenerally O-ring in shape and formed from a suitable selflubricatingnylon type material.

The bearing tube 12 receives chair seat spindle 22 that is suitablythreaded as at 24 for threaded cooperation with the nut or hand wheel 26which is formed to receive, rest on, and be keyed to, swivel member 28that engages the bearing element 20 in the manner indicated in FIG. 1.

The bearing retaining portion 18 of the bearing tube 12 defines abearing seat 30 and the swivel member 28 defines a bearing seat 32 whichare the means whereby the bearing element is supported and verticalloads supplied to the seat are transmitted to the bearing element,respectively. It is to be noted that the bearing seats 30 and 32 areshaped to substantially complement the surface portions of the bearingelement 20 that engage same. Bearing element 20, in accordance with thisinvention, is generally of the simplified O-ring or torus (sometimescalled anchor ring) shape indicated in FIG. 7, except that it is splitas at 34 whereby the bearing element has a self centering action withrespect to the bearing seats that engage same under the loads appliedagainst it to accommodate tolerance variations. Bearing element 20,retaining portion I8 of bearing tube l2, and swivel member 28 form abearing unit 25.

Swivel member 28 is formed with lug 36 that is lodged in slot 38 ofchair base spindle 22, and is shaped to define upwardly directed ridgesor protuberances 40 adapted to seat in correspondingly located recessesor notches 42 formed in hand wheel or nut 26 (see FIGS. ,3, 4 and 6).

In the form shown, the bearing tube l2 is received within an inner shell44 that is fixed at its lower end 46 to the conventional chair base legs48, in a manner similar to that shown in Buhrmaster U.S. Pat. No.3,186,669. The inner shell 44 carries at its upper end 50 a starredwasher 52 on which rests a collar 54 against which the bearing tubeupper end rests, and

which reinforces the upper end of the bearing tube 12.

Received over the inner shell 44 is an outer decorative shell S6 havingan outer diameter complementing that of the nut or hand wheel 26, andwhich is held centered with respect to the inner shell at the upper endof the bearing tube by the triangular flanges 58 of the washer 52. Thelower end of the outer tube 56 is slotted as at 60, in a matter similarto that shown in said Buhrmaster patent, to receive the chair base legs48.

Spindle 22 is suitably formed at its upper end 62 for securement to achair seat (a portion of which is shown in dashed lines at 63), andcarries a sleeve bearing 64 at its lower end 66 that is received withinthe bearing tube and has an outer diameter that substantiallycomplements the inner diameter of the bearing tube.

lt will thus be seen that in normal operation, the weight of the chairseat and its load is transmitted to the chair base 14 through spindle22, nut or hand wheel 26, swivel member 28, bearing element 20, and thebearing tube 12 from which the load is transmitted to the inner shell 44and legs 48.

In normal use, when the chair seat is swiveled, the nut i and swivelmember 28 rotate with spindle 22, relative to the bearing tube 12. Thebearing arrangement illustrated provides two slip or wear surfaces atthe respective bearing seats 30 and 32 to accommodate this swivelingaction. Under ordinary circumstances, bearing element 20 will remainstationary with respect to the bearing tube and the swivel member 28will swivel with respect to the bearing element since the area ofcontact between seat 30 and the bearing element 28 exceeds the area ofcontact between the seat 32 and the bearing element. However, thealternate slip or wear surface represented by the engagement of bearingelement 28 with seat 30 is available to accommodate swiveling movementof the chair seat in the event that the frictional relationships betweenthe bearing element and seat 30 are such that the bearing elementswivels with the swivel member 28.

It is to be noted that the bearing element 20 is substantiallycontinuous about its circumference, except at the slit 34, whichprovides a substantially continuous and uninterrupted load supportingfunction about the seats 30 and 32. Seats 30 and 32 havingconfigurations substantially complementing the external surface of thebearing element, and the bearing element 34 being split, results in auniform load supporting action about the circumference of the spindledue to the self centering action on the bearing element. The bearingsleeve 64 resists lateral thrusts acting on spindle 62.

When one desires to adjust the elevation of the seat with regard to thechair base 14, the spindle 22 is held from rotation by grasping thechair seat 63 and the hand wheel 26 is rotated in 90 increments whichare the result of the ridges 40 of swivel member 28 mating with notches42 of the hand wheel 26. This action raises or lowers the spindle withrespect to the hand wheel depending on the direction of rotation. Screw70 acts as a retainer for the hand wheel 26 to keep the base assembledto the chair when the chair is lifted by its arms. In normal swivelaction the retaining screw 70 is not functional.

In the embodiment 10A of FIG. 8, the seat 30A defined by the bearingtube 12A is formed in a hub assembly 80 in which the hub assembly 80includes collar portion 54A that is integrally united with bearingretainer portion 18A. Hub assembly 80 is applied to the upper end 16A ofthe bearing tube.

The device 10A is otherwise the same as device l0.

SPECIFIC DESCRIPTION Referring back to device l0, the bearing tube 12may be formed from any suitable metallic substance such as suitabletubing steel defining tubular member 82 that has the bearing portion 18suitably formed in its upper end 16 to the configuration indicated inFIG. 1.

As indicated in FIG. 1, the external diameter of the shank portion ofthe bearing tube 12 is proportioned to substantially complement or fitclosely inside the internal surface 84 of the inner shell 44, which islikewise made of any suitable metallic substance such as tubing steel.The lower end 91 of the bearing tube has applied thereto a hub cap 92and both are suitably fixed to the inner shell 44, as by welding at 94.Preferably the joint between the cap 92 and the lower end of bearingtube 17 is made leak free to retain within the bearing tube l2 anylubricant that is applied to the bearing units 25 and 64.

At the upper end 16 of the bearing tube l2, the starred washer 52includes a rounded rim portion 96 that rests on the upper end 50 of theinner shell and deflnes a bore 98 through which the bearing tube l2projects. The pointed or triangular flanges 58 are four in number andare spaced equidistant about the circumference of the washer 52 so thatopposed flanges 58 are 180 degrees apart. The flanges 58 are deflecteddownwardly, as indicated in FIG. l, such that when the outer shell 56 isapplied thereto, the flanges 58 are deflected radially inwardly somewhatso that their respective edge corners 100 bear firmly against the innersurface 102 of the outer shell 56 for firm centering purposes.

The inner shell 44, the washer 52, and the collar 54 are joined bywelding as at 104 between flanges 58 in at least two places apart orpreferably at four places between each adjacent pair of flanges 58.

The collar 54 has internal and external diameters substantiallyidentical to those of the inner shell 44, and is proportioned axially ofthe inner shell to space the bearing element 20 as desired above thefloor on which the chair is to rest. In applying the bearing tube l2 tothe inner shell, the bearing tube 12 is moved downwardly of the innershell until its retainer portion 18 rests against the end 106 of thecollar, with the other end 108 of the collar resting on washer 52.

As already indicated, the inner shell 44 is suitably welded to the chairbase legs 48, and the welds are substantially covered by the outer shell56.

Spindle 22 is formed from any suitable metallic material such as mildsteel. Upper end 62 is suitably formed for application to a chair seat63 in any conventional manner, and threading 24 may be of any suitabletype best adapted for purposes of this invention. Slot 38 extendslongitudinally of the spindle through the threading 24 and isproportioned to receive lug 36 of the swivel member 28 for slidingadjustment of member 28 longitudinally on the spindle 22.

The sleeve bearing 64 may be of any suitable type, for instance nylon orpolyethylene, and made in the form of a tube 111 press fitted ontospindle 22. Alternately, the sleeve bearing may be moulded directly onthe spindle 22. The exterior surface 112 of the bearing 64 should belightly greased before application into bearing tube 12. The surface 112should have a diameter substantially complementing the internal diameterof the bearing tube shank 90 for close fitting relation thereto.

The nut or hand wheel 26 is formed from any suitable material, itcomprising a zinc die cast structure in the illustrated embodiment,having its outer surface 120 suitably chrome plated. Hand wheel 26defines a body 122 having a bore 124 internally threaded as at 126 forthreaded cooperation with the threading 24 of spindle 22. Thebodyincludes a depending skirt 128 that masks the bearing unit 25 in theassembled relation of same. Screw 70 is suitably applied to threadedopening 130 in the skirt 28.

The body 122 and its skirt 128 define a socket 132 in which the bearingunit 25 is received. Socket 132 is defined by the internal side wall 134of skirt 128 and a base wall 136 which is suitably indented to definenotches or recesses 42 that are proportioned to receive the ridges 40 ofswivel member 28. The notches 42 each have on either side of same angledsurfaces 140 (see FIG. 6) that serve to guide the respective ridges 40into the respective recesses 42.

The swivel member 28 in the form shown comprises an annular sinteredmember 150 formed from a material suitable for this purpose. In onecommercial embodiment, member 150 is ASTM B426-68 type III grade l oilimpregnated sintered copper steel having a hardness on the order ofRockwell B 65.

Body 150 is shaped to define lug 36, ridges 40, and define a bore 152that closely receives the threading 24 of spindle 22 (see FIG. l). Body150 is formed with annular internal shoulder 154 that defines bearingseat 32 and end portion or extension 156 which is received within thebearing element 20.

The bearing element is preferably formed from a suitable selflubricating type material (for instance, nylon type products, such asthat sold under the trademark DELRIN by E. I. Du Pont De NemoursCompany, Wilmington, Del. [Delfin 100 being employed in a commercialembodiment of the invention]). Bearing element 20 is preferably of thesimplified torus or anchor ring configuration that is illustrated andthus has the circular transverse cross-sectional configuration that isshown in FIG. 1, which bearing seats 30 and 32 substantially complement.Bearing element 20 is in the form of O-ring 160, which in the formillustrated, is split axially thereof, as at 34 (see FIG. 7) to defineend portions 164 and 166 that are separated but in closely spacedrelation.

While the invention contemplates that unsplit O- rings ofthe typeindicated may be employed, the split ring type is preferred so thattolerance variations in making the parts that define bearing seats 30and 32 are accommodated, the general shape of the seats 30 and 32, whenthe bearing is assembled, tending to cam the ring into properly centeredrelation with respect to the cam surfaces and 32.

It is preferable, however, that the ring 160 be substantially continuousabout the circumferences of seats 30 and 32, and for this reason thesplit 34 should be of small dimension (circumferentially of ring 160)that is limited to be adequate to insure the lateral adjustability thatis desired. In a commercial embodiment, the ends 160 and 164 areseparated by a space of three thirtyseconds inch, in a ring 160 havingan internal diameter of 1.182 inches, and an external diameter of l l1/l6ths inches and a cross section of 1//4 inch diameter.

Bearing seat 30 is defined by the retainer portion 18 of the bearingtube 12, which has the cupped configuration shown in FIG. 1 defined byan internal shoulder and saucer shaped rim portion 172 that is shaped tosubstantially complement the configuration of the external surface 165of ring 160 (excluding split 34). Rim portion 172 terminates in an edgeportion 174 that projects axially from the bearing tube somewhat abovethe center line 176 of the bearing element (see FIG. 1), approximatelyto the extent that the extension 156 of the swivel member 28 projectsbelow the center line 176 of the bearing element.

The portions of the bearing seats 30 and 32 which contact the surface165 of the bearing element 20 may be considered to be semi-torus oranchor ring shaped in cross-sectional configuration in view of themanner that they lap around a substantial portion of the surface 165 ofthe bearing element. It is to be noted that the seat 30 engages thelower one quarter or quadrant surface on the outer side of the bearingelement while the seat 32 engages the upper one quarter or quadrantsurface on the inner side of the bearing element.

In the device 10A, the bearing tube 12A is a two part structureincluding the combination retainer portion and collar assembly or member80, which is shouldered as at 180 to rest on the end 182 of the bearingtube 12A. Member 80 is formed from any suitable mild steel and ismachined to the shape indicated, it thereby defining a socket 184 inwhich the upper end 16A of the bearing tube is received.

Member 80 is of cup shaped configuration defining a base wall 186 thatis bored as at 188 to receive the spindle threading 24, wall 186 beingsuitably relieved as at 190. Wall 186 includes an axially extending rimportion 192 shaped to define seat 30A and an axially extending flangeportion 194 which forms the collar 54A.

Member 80 after being applied to tube 12A in the manner indicated inFIG. 8, on top of starred washer 52, is suitably spot welded to thebearing tube, and member 80, the washer and the bearing tube are weldedtogether at the same locations as in the device 10 (see weld 104).

The device 10A is otherwise the same as device 10.

It will therefore be seen that the invention provides a chair baseswivel arrangement for swivel chairs of highly simplified constructionrequiring a bearing element of minimum size and simplified nature. Thecomplementary nature of the bearing element20 and the seats 30 and 32which engage same, together with the self adjusting nature of thebearing element provided by its split 162, insures a continuous area ofcontact about the circumference of the bearing between its split ends164 and 166 along the opposed quadrant areas of the bearing ringcircumferential surface that have been indicated. Only nominallubrication is required for this invention as the material from whichthe bearing element is formed is self lubricating in nature. However, itis preferred that when the parts are assembled that the bearing seat 30be lightly greased to insure that the two possible slip or wear surfacescontemplated by this invention are available. Also, swivel member 28 maybe oil impregnated, if desired. As already indicated, since the area ofcontact between the bearing element 20 and seat 32 is of less area thanthe area of contact between the bearing element and bearing seat 30,normally the bearing element 20 will remain stationary on swiveling ofthe chair seat, and the parts that are fixed to same for rotationtherewith, which includes the spindle 22, the swivel member 28, and thenut or hand wheel 26 when it is resting in interlocked relation with theswivel member 28. Having a slip or wear surface at the seat 30 makes fora more readily swivelable chair seat.

However, the slip or wear surface at the bearing seat 30 is alwaysavailable in the event that the bearing element 20 becomes adhered tothe seat 32 sufficiently so that slippage occurs at the seat 30 ratherthan at the seat 32.

lt should also be noted that both slip surfaces provided by seats 30 and32 are greater than what would be available if the bearing surfacebetween the spindle and its support was at the outer surfaces 195 of thespindle threading 24. Furthermore, bearing element 20 is not only wellspaced from the spindle threading, but is protected from it by swivelmember end portion 156, which avoids undesirable contact between thebearing element and the spindle threads that could result in shaving ofthe bearing element or other premature wear.

As the bearing element 20 is not keyed to the spindle 22 in any way, itsshape may be the simple O-ring or torus configuration that is indicated.

Tests of the swivel arrangement illustrated indicates that itsatisfactorily withstands torture tests of the type applying a 250 poundload six inches off the center of the center line of the spindle, withthe spindle being rotated relative to the base at approximately 30 rpmfor 120,000 cycles.

The foregoing description and the drawings are given merely to explainand illustrate the invention and the invention is not to be limitedthereto, except insofar as the appended claims are so limited, sincethose skilled in the art who have the disclosure before them will beable to make modifications and variations therein without departing fromthe scope of the inention.

We claim:

1. A chair base swivel arrangement comprising:

a base structure including an upright tubular member carrying an annularbearing seat at its upper end,

a one piece bearing element of anchor ring configuration and formed fromantifriction material seated on said seat in substantial concentricrelation therewith,

a swivel member seated on said bearing element and including a bearingseat engaging said bearing element,

said seats and said element lying in substantially parallel planes thatare substantially normal to the axes thereof,

a chair seat having a threaded spindle received in said tubular member,

a nut removably seated on said swivel member and threadedly engaged withsaid spindle,

means for keying said swivel member against rotational movement relativeto said spindle,

and means for releasably keying said nut to said swivel member,

said bearing seats defining substantially continuous and uninterruptedbearing surfaces for engaging said bearing element that substntiallycomplement the surface portions thereof that are engaged thereby,

said tubular member seat engaging the lower outer quadrant of saidbearing element surface.

and said swivel member seat engaging the inner upper quadrant of saidbearing element surface,

said bearing element being interrupted to define two end portions inclosely spaced relation whereby when said bearing element is engaged bysaid bearing seats said bearing element is biased into conformitytherewith,

a post structure in which said tubular member is received and aplurality of leg elements fixed to and extending laterally of said poststructure,

said post structure comprising:

an inner shell to which said leg elements are fixed,

an outer shell received over said inner shell in substantial concentricrelation therewith and receiving said leg elements,

said tubular member extending through said inner shell at either end ofthe latter,

a cap closing off said tubular member at the lower end of same,

and means for fixing said tubular member to said inner shell at thelower end of same,

a starred washer applied to the upper end of said inner shell and withinsaid outer shell,

said washer including triangular projections of equal radial lengthsspaced thereabout engaging said outer shell,

and a collar applied between said tubular member seat and said washerfor supporting said tubular member seat on the upper end of said innershell.

2. The swivel arrangement set forth in claim l wherein:

said tubular member bearing seat is integral there with. 3. The swivelarrangement set forth in claim 1 wherein:

said tubular member seat comprises:

a hub member received on the upper end of said tubular member,

said hub member including said collar and being formed to define saidtubular member seat.

4. The swivel arrangement set forth in claim 1 wherein:

said nut includes a skirt depending therefrom disposed in maskingrelation about said tubular member bearing seat and said collar,

said nut skirt and said outer shell being of substantially equaldiameters and being in coaxial relation.

5. A chair base swivel arrangement comprising:

a base structure including an upright tubular member carrying an annularbearing seat at its upper end,

a one piece bearing element of anchor ring configuration and formed fromantifriction material seated on said seat in substantial concentricrelation therewith,

a swivel member seated on said bearing element and including a bearingseat engaging said bearing element,

said seats and said element lying in substantially parallel planes thatare substantially normal to the axes thereof,

a chair seat having a threaded spindle received in said tubular member,

a nut removably seated on said swivel member and threadedly engaged withsaid spindle,

means for keying said swivel member against rotational movement relativeto said spindle,

and means for releasably keying said nut to said swivel member,

said bearing seats defining substantially continuous and uninterruptedbearing surfaces for engaging said bearing element that substantiallycomplement the surface portions thereof that are engaged thereby,

said tubular member seat engaging the lower outer quadrant of saidbearing element surface,

and said swivel member seat engaging the inner upper quadrant of saidbearing element surface,

a post structure in which said tubular membber is received and aplurality of leg elements fixed to and extending laterally of said poststructure,

said post structure comprising:

an inner lshell to which said leg elements are fixed,

an outer shell received over said inner shell in sub stantial concentricrelation therewithrand receiving said leg elements,

said tubular member extending through said inner shell at either end ofthe latter,

and means for fixing said tubular member to said inner shell at thelower end of same,

a starred washer applied to the upper end of said inner shell and withinsaid outer shell,

said washer including projections of equal radial lengths spacedthereabout said outer shell,

and an annular support applied between said tubular member seat and saidwasher for supporting said tubular member seat on the upper end of saidinner shell.

6. In a swivel arrangement for chair bases of the type supporting achair seat spindle, having a threaded portion, from a base structure, inwhich the swivel arrangement includes a tubular member receiving thespindle, means supporting said tubular member in upright position fromsaid base structure, said tubular member having an upwardly facingannular bearing seat at its upper end, a bearing means seated on saidbearing seat in substantial concentric relation therewith, a swivelmember seated on said bearing means and including a downwardly facingannular bearing seat engaging said bearing means, a nut removably seatedon said swivel member and including internal threading for threadedconnection with the spindle threaded portion for supporting the latteron said tubular member, means for releasably keying said nut to saidswivel member, and means for keying said swivel member againstrotational movement relative to the spindle, the improvement wherein:said bearing means comprises a one piece torus shaped element formedfrom antifriction material and having a torus shaped'external surface,

with said bearing element'being free of keying connection to saidspindle and to said seats,

said bearing seats each being of concave semitorus configurationsubstantially complementing the configuration of the surface portions ofsaid bearing element they engage and each being proportioned to engageapproximately an annular quadrant of said external surface of saidbearing element, said bearing seats and said bearing element beingspaced laterally of and about said spindle,

said tubular member seat engaging the lower outer quadrant of saidbearing element surface,

and said swivel member seat engaging the inner upper quadrant of saidbearing element surface and being shaped to shield said bearing elementfrom said spindle threaded portion,

wherebyv said swivel member seat and said bearing element define a firstnormally operative slip surface therebetween and said bearing elementand said tubular member seat define a second contingency slip surfacetherebetween of greater area than said first slip surface,

and whereby said seats and said bearing element are in vertical andradial thrust transmitting relation.

7. The improvement set forth in claim 6 wherein:

said bearing element is split axially thereof to define two opposed endportions in closely spaced relation,

said bearing element being free to flex laterally thereof whereby saidseats cam said element into centered relation therewith to accommodatetolerance variations.

8. The improvement set forth in claim 6 wherein said base structurecomprises:

a post structure in which said tubular member is received and aplurality of leg elements fixed to and extending laterally of said poststructure,

said post structure comprising:

an inner shell to which said leg elements are fixed,

an outer shell received over said inner'shell in substantial concentricrelation therewith and receiving said leg elements,

said tubular member extending through said inner shell at either end ofthe latter,

and means for fixing said tubular member to said inner shell at thelower end of same,

a starred washer applied to the upper end of said inner shell and withinsaid outer shell,

said washer including projections of equal radial lengths spacedthereabout engaging said outer shell,

and an annular support applied between said tubular member seat and saidwasher for supporting said tubular member seat on the upper end of saidinner shell.

1. A chair base swivel arrangement comprising: a base structureincLuding an upright tubular member carrying an annular bearing seat atits upper end, a one piece bearing element of anchor ring configurationand formed from antifriction material seated on said seat in substantialconcentric relation therewith, a swivel member seated on said bearingelement and including a bearing seat engaging said bearing element, saidseats and said element lying in substantially parallel planes that aresubstantially normal to the axes thereof, a chair seat having a threadedspindle received in said tubular member, a nut removably seated on saidswivel member and threadedly engaged with said spindle, means for keyingsaid swivel member against rotational movement relative to said spindle,and means for releasably keying said nut to said swivel member, saidbearing seats defining substantially continuous and uninterruptedbearing surfaces for engaging said bearing element that substntiallycomplement the surface portions thereof that are engaged thereby, saidtubular member seat engaging the lower outer quadrant of said bearingelement surface, and said swivel member seat engaging the inner upperquadrant of said bearing element surface, said bearing element beinginterrupted to define two end portions in closely spaced relationwhereby when said bearing element is engaged by said bearing seats saidbearing element is biased into conformity therewith, a post structure inwhich said tubular member is received and a plurality of leg elementsfixed to and extending laterally of said post structure, said poststructure comprising: an inner shell to which said leg elements arefixed, an outer shell received over said inner shell in substantialconcentric relation therewith and receiving said leg elements, saidtubular member extending through said inner shell at either end of thelatter, a cap closing off said tubular member at the lower end of same,and means for fixing said tubular member to said inner shell at thelower end of same, a starred washer applied to the upper end of saidinner shell and within said outer shell, said washer includingtriangular projections of equal radial lengths spaced thereaboutengaging said outer shell, and a collar applied between said tubularmember seat and said washer for supporting said tubular member seat onthe upper end of said inner shell.
 2. The swivel arrangement set forthin claim 1 wherein: said tubular member bearing seat is integraltherewith.
 3. The swivel arrangement set forth in claim 1 wherein: saidtubular member seat comprises: a hub member received on the upper end ofsaid tubular member, said hub member including said collar and beingformed to define said tubular member seat.
 4. The swivel arrangement setforth in claim 1 wherein: said nut includes a skirt depending therefromdisposed in masking relation about said tubular member bearing seat andsaid collar, said nut skirt and said outer shell being of substantiallyequal diameters and being in coaxial relation.
 5. A chair base swivelarrangement comprising: a base structure including an upright tubularmember carrying an annular bearing seat at its upper end, a one piecebearing element of anchor ring configuration and formed fromantifriction material seated on said seat in substantial concentricrelation therewith, a swivel member seated on said bearing element andincluding a bearing seat engaging said bearing element, said seats andsaid element lying in substantially parallel planes that aresubstantially normal to the axes thereof, a chair seat having a threadedspindle received in said tubular member, a nut removably seated on saidswivel member and threadedly engaged with said spindle, means for keyingsaid swivel member against rotational movement relative to said spindle,and means for releasably keying said nut to said swivel member, saidbearing seats defining substantially continuous and uninterruptedbearing surfaces for engaging said bearing element that substantiallycomplement the surface portions thereof that are engaged thereby, saidtubular member seat engaging the lower outer quadrant of said bearingelement surface, and said swivel member seat engaging the inner upperquadrant of said bearing element surface, a post structure in which saidtubular membber is received and a plurality of leg elements fixed to andextending laterally of said post structure, said post structurecomprising: an inner shell to which said leg elements are fixed, anouter shell received over said inner shell in substantial concentricrelation therewith and receiving said leg elements, said tubular memberextending through said inner shell at either end of the latter, andmeans for fixing said tubular member to said inner shell at the lowerend of same, a starred washer applied to the upper end of said innershell and within said outer shell, said washer including projections ofequal radial lengths spaced thereabout said outer shell, and an annularsupport applied between said tubular member seat and said washer forsupporting said tubular member seat on the upper end of said innershell.
 6. In a swivel arrangement for chair bases of the type supportinga chair seat spindle, having a threaded portion, from a base structure,in which the swivel arrangement includes a tubular member receiving thespindle, means supporting said tubular member in upright position fromsaid base structure, said tubular member having an upwardly facingannular bearing seat at its upper end, a bearing means seated on saidbearing seat in substantial concentric relation therewith, a swivelmember seated on said bearing means and including a downwardly facingannular bearing seat engaging said bearing means, a nut removably seatedon said swivel member and including internal threading for threadedconnection with the spindle threaded portion for supporting the latteron said tubular member, means for releasably keying said nut to saidswivel member, and means for keying said swivel member againstrotational movement relative to the spindle, the improvement wherein:said bearing means comprises a one piece torus shaped element formedfrom antifriction material and having a torus shaped external surface,with said bearing element being free of keying connection to saidspindle and to said seats, said bearing seats each being of concavesemitorus configuration substantially complementing the configuration ofthe surface portions of said bearing element they engage and each beingproportioned to engage approximately an annular quadrant of saidexternal surface of said bearing element, said bearing seats and saidbearing element being spaced laterally of and about said spindle, saidtubular member seat engaging the lower outer quadrant of said bearingelement surface, and said swivel member seat engaging the inner upperquadrant of said bearing element surface and being shaped to shield saidbearing element from said spindle threaded portion, whereby said swivelmember seat and said bearing element define a first normally operativeslip surface therebetween and said bearing element and said tubularmember seat define a second contingency slip surface therebetween ofgreater area than said first slip surface, and whereby said seats andsaid bearing element are in vertical and radial thrust transmittingrelation.
 7. The improvement set forth in claim 6 wherein: said bearingelement is split axially thereof to define two opposed end portions inclosely spaced relation, said bearing element being free to flexlaterally thereof whereby said seats cam said element into centeredrelation therewith to accommodate tolerance variations.
 8. Theimprovement set forth in claim 6 wherein said base structure comprises:a post structure in which said tubular member is received and aplurality of leg elements fixed to and extending laterally of said poststructure, said post structure comprising: an inner shell to which saidleg elements are fixed, an outer shell received over said inner shell insubstantial concentric relation therewith and receiving said legelements, said tubular member extending through said inner shell ateither end of the latter, and means for fixing said tubular member tosaid inner shell at the lower end of same, a starred washer applied tothe upper end of said inner shell and within said outer shell, saidwasher including projections of equal radial lengths spaced thereaboutengaging said outer shell, and an annular support applied between saidtubular member seat and said washer for supporting said tubular memberseat on the upper end of said inner shell.